Neutrophils are primary source of O-2 radicals during reperfusion after prolonged myocardial ischemia

Although many studies document oxygen radical formation during ischemia-rep erfusion, few address the sources of radicals in vivo or examine radical ge neration in the context of prolonged ischemia. In particular, the contribut ion of activated neutrophils remains unclear. To investigate this issue, we developed a methodology to detect radicals without interfering with blood- borne mechanisms of radical generation. Dogs underwent aorta and coronary s inus catheterization. No chemicals were infused; instead, blood was drawn i nto syringes prefilled with a spin trap and analyzed by electron paramagnet ic resonance spectroscopy. After 90 min of coronary artery occlusion, trans cardiac concentration of oxygen radicals rose severalfold 10 min after refl ow and remained significantly elevated for at least 1 h. Radicals were most ly derived from neutrophils, as shown by marked reduction after the adminis tration of 1) neutrophil NADPH oxidase inhibitors and 2) a monoclonal antib ody (R15.7) against neutrophil CD18 adhesion molecule. Reduction of radical generation by R15.7 was also associated with a significantly smaller infar ct size and no-reflow areas. Thus our data demonstrate that neutrophils are a major source of oxidants in hearts reperfused in vivo after prolonged is chemia and that antineutrophil interventions can effectively prevent the in crease in oxygen radical concentration during reperfusion.